The present invention relates to a cooling system and in particular to a cooling system used in an application in which a high coolant pressure and high delivery velocity is desired. One such application is in the machine tools where a cutting fluid is provided to cool and lubricate the tool and workpiece and to wash away cut chips.
Typical machine tool coolant systems produce a coolant pressure estimated at between 15 and 30 psi at the pump outlet which is delivered to the tooling and workpiece with a relatively large diameter outlet. The coolant is delivered to the cutting site through outlets varying in diameter from one quarter to one inch and possibly more. The number of coolant lines used varies depending upon the number and nature of machining operations. With typical cooling systems, the coolant impacts the tooling and workpiece with relatively little velocity and at low pressure to flood the workpiece. During some machine operations such as drilling or boring, the accessibility to the cutting location is extremely limited. With flooding type coolant delivery, the low velocity and low pressure coolant may not reach the cutting surface. The result is that cutting is typically performed dry or with inadequate cooling and lubricating. This produces high cutting temperatures and wear resulting in short tool life, necessitating frequent tooling changes and consequent machine down time. In addition, the flood coolant flow may not be adequate to remove the metal chips at the point of cutting. The chips may interfere with the cutting operation producing a surface finish of lower quality than desired.
In an effort to improve the delivery of coolant with certain tools, e.g. drills, tools have been developed with a coolant passages extending through the tool itself to deliver coolant to the cutting surface. This however, adds significantly to the cost of the tool and machine. Furthermore, due to the relatively low fluid pressures utilized, insufficient pressure is often provided to remove chips from the coolant passage such that coolant flow is blocked.
It is known that high temperature and lack of lubrication are the primary causes of tool wear. If cooling and lubrication can be increased, tool life will be extended, reducing the manufacturing cost. Cost is reduced by fewer tools needed to produce a given quantity of parts, less machine down time for tool changes and less operator time required to change tools.
Accordingly, it is an objective of the present invention to improve the cooling system of a machine tool to reduce tool and workpiece temperatures and to improve lubrication.
It is a feature of the present invention to use small coolant spray streams from spray nozzles and to direct the spray streams precisely to the cutting locating rather than to flood the workpiece and tool with coolant.
It is another feature of the present invention to provide high pressure and high velocity coolant flow to force the coolant to hard to reach cutting locations to improve cooling and lubrication.
By providing increased pressure and velocity to the coolant flow, the coolant is forced into locations not reached with low pressure flooding cooling systems. This provides numerous advantages such as improved removal of the cut chips from the cutting location, the temperature of both the workpiece and the tooling is reduced and tooling wear is reduced. These advantages can be manifested in many ways such as: elimination of the need for coated tooling in many applications; elimination of through-the-tool coolant passages; longer tool life before grinding and less material removal during grinding; decreased machine cycle time resulting from faster machining; reduced number of tools from the tooling set up; less operator time per machine allowing one person to operate more machines; and improved surface finish reducing the need for grinding. The advantages derived from improved cooling can be applied in many ways depending on what factors are to be maximized.
The cooling system of the present invention also improves the coolant filter set up. A disadvantage with many currently used cooling systems pertains to the filter used to remove chips from the coolant. The filters are frequently permanently installed in the coolant reservoir, necessitating that the machine operator reach into the reservoir to remove accumulated chips from the filter. For many machine operators, excessive skin contact with the coolant can cause dermatitis. Further, because the coolant is often hot, it can produce burns. If a thorough cleaning of the filter is required, the operator must remove the filter from the coolant reservoir, necessitating machine down time of as much as five to thirty minutes.
Accordingly, it is a further objective of the present invention to provide a coolant system having a filter that minimizes operator contact with the coolant for filter cleaning and that reduces machine down time required for filter cleaning.
The advantage of minimizing operating contact with the coolant is a safer environment for the operator. By reducing machine down time for filter cleaning, productivity can be increased.
The cooling system of the present invention accomplishes these objectives by utilizing a positive displacement pump together with small orifice nozzles at the coolant discharge. This provides for a high velocity coolant discharge and creation of high pump outlet pressure while maintaining a large coolant flow rate.
The coolant filter on the intake side of the pump is mounted by a flexible hose enabling the filter to be readily removed from the coolant reservoir for cleaning, thereby eliminating the need for the machine operator to reach into the coolant reservoir. Furthermore, the filter is coupled to the inlet hose with a quick connect/disconnect coupling. By utilizing two filters per machine, an operator can quickly remove a dirty filter and install a clean filter, returning the machine to operation in a minimal length of time. After filter change, the dirty filter is cleaned while the machine is operating and is available for use when the next filter cleaning is required.
Further objects, features and advantages of the invention will become apparent from a consideration of the following description and the appended claims when taken in connection with the accompanying drawings.